Grid-connected power generation systems typically include two major parts: power generators that produce the power and inverters that receive, condition, and inject the power into the power distribution grid. Power generators include, for example, photovoltaic (PV) cells and wind turbines.
Power generators may be configured as: centralized, string, multi-string, and AC-module/cell technologies. To increase the overall efficiency of power generators under different conditions, such as varying wind conditions on wind turbines, partial shadowing of PV cells, or mismatches between PV cells, independent control and power extraction is required for each power generator. This requires using a separate inverter, i.e., a micro-inverter”, for each power generator. Power extraction from each power generator may enhanced if maximum power point tracking (MPPT) is be performed on each power generator independently.
Maximum power point tracking of a PV cell in particular is challenging due to the nonlinear current-voltage characteristic and ever-changing nature of the irradiation source. Conventional MPPT systems use an algorithm that finds the best operating point and creates a reference signal, or logical and relational operators, and are based on trial and error or seek and find to find the best operating point. These may be implemented in software running on microprocessors. Such approaches may lead to oscillation around the optimum point, which adversely impacts overall efficiency of the system. Moreover, trial and error approaches degrades efficiency for fast changing conditions. This drawback and the low speed characteristic of such approaches may be problematic in conditions such as monotonic and fast increase of the irradiation level.